DataInput与DataOutput

习惯了读写字符串时用PrintWriter和BufferedReader

PrintWriter(BufferedWriter(OutputStreamWriter(OutputStream)))

BufferedReader(InputStreamReader(InputStream))

这两天给别人看项目代码的时候看到程序里用了readUTF和writeUTF这两个方法，顿时从尘封的记忆中唤起DataInput和DataOutput这两个接口。好久不用，我都快把它俩给忘了。

项目运行的时候老是会抛出EOFException，不明白怎么回事，因而看了看JDK文档，本身写了一段小程序测试了一下，猜想readUTF方法彷佛是经过抛出EOFException来代表到达数据的末尾，如同bufferedReader.readLine()经过返回null代表到达数据的结尾同样，只是表达的方式不一样而已。所以只须要经过检查EOFException异常来结束程序便可。

EOFException文档中提到：

    此异常主要被数据输入流用来代表到达流的末尾。注意，其余许多输入操做返回一个特殊值表示到达流的末尾，而不是抛出异常。

如下是我写的测试代码：（Java6）

服务端：

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Socket socket = null;
		DataInputStream in = null;
		DataOutputStream out = null;
		try {
			socket = new Socket("localhost", 10011);
			out = new DataOutputStream(socket.getOutputStream());
			in = new DataInputStream(socket.getInputStream());
			for (int i = 0; i < 100; i++) {
				out.writeUTF("aaa1");
				out.flush();
				System.out.println(in.readUTF());
			}
			in.close();
			out.close();
			socket.close();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (in != null) {
				try {
					in.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if (out != null) {
				try {
					out.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if (socket != null) {
				try {
					socket.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

}

客户端：

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class Server {
	static class ReadTask implements Runnable {
		private final Socket so;

		public ReadTask(Socket so) {
			this.so = so;
		}

		@Override
		public void run() {
			DataInputStream in = null;
			DataOutputStream out = null;
			try {
				in = new DataInputStream(this.so.getInputStream());
				out = new DataOutputStream(this.so.getOutputStream());
				System.out.println("开始处理");
				while (true) {
					String cmd = in.readUTF();
					// do some work
					TimeUnit.MILLISECONDS.sleep(10);
					out.writeUTF("result -- " + cmd);
				}
			} catch (EOFException e) {
				System.out.println("处理完成");
			} catch (IOException e1) {
				e1.printStackTrace();
			} catch (InterruptedException e) {
				Thread.currentThread().interrupt();
			} finally {
				if (in != null) {
					try {
						in.close();
					} catch (IOException e) {
						e.printStackTrace();
					}
				}
				if (out != null) {
					try {
						out.close();
					} catch (IOException e) {
						e.printStackTrace();
					}
				}
				if (this.so != null) {
					try {
						this.so.close();
					} catch (IOException e) {
						e.printStackTrace();
					}
				}
			}
		}
	}

	/**
	 * @param args
	 * @throws InterruptedException
	 */
	public static void main(String[] args) throws InterruptedException {
		ExecutorService exec = Executors.newCachedThreadPool();
		ServerSocket server = null;
		try {
			server = new ServerSocket(10011);
			System.out.println("server started");
			while (true) {
				Socket socket = server.accept();
				ReadTask task = new ReadTask(socket);
				exec.execute(task);
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			exec.shutdown();
			exec.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);
			if (server != null) {
				try {
					server.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
}